Methods of microscopically inspecting opposite sides of objects

ABSTRACT

Microscopic inspection of objects such as beam-lead integrated circuits is accomplished by positioning the objects mounted on platforms in a spaced relationship under a vacuum pickup needle located in the field of view of the microscope. Rapid and accurate positioning is aided by air bearing facilities. One of the platforms includes a transparent disc for supporting the bottom sides of the objects. The disc is parallel to and spaced from a mirror which reflects an image of the bottom sides to the microscope. The microscope is first raised to its upper position along its principal axis and focused on the top sides of the objects so that the mirror image of the bottom sides is out of focus and not visible. The top sides are then individually inspected. Next, the microscope is moved to its lower position along its axis and then focused on the mirror image of the bottom sides of the objects so that the top sides are out of focus. Preferably, the magnification of the microscope while in its lower position is increased to provide a larger image of the bottom sides to thereby facilitate their inspection. The increasing of the magnification also decreases the depth of field of the microscope so that an image of the top sides is far out of focus and therefore not visible. This improves the clarity of the image of the bottom sides to further facilitate their inspection. The bottom sides are then individually inspected. During the inspection the objects are separated in accordance with certain characteristics with the aid of a vacuum pickup needle. The movement of the needle is limited by a ball plunger to prevent damage to the objects.

United State Wanesky Feb. 26, 1974 METHODS OF MICROSCOPICALLY INSPECTINGOPPOSITE SIDES OF OBJECTS [75] Inventor: William R. Wanesky,Wescosville,

[73] Assignee: Western Electric Company, I

Incorporated, New York, NY.

[22] Filed: May 18, 1972 [21] Appl. No.: 254,550

Related US. Application Data [62] Division of Ser. No. 30,379, April 21,1970, Pat. No.

Primary Examiner-David H. Rubin Attorney, Agent, or FirmR. Y. Peters[57] ABSTRACT Microscopic inspection of objects such as beam-leadintegrated circuits is accomplished by positioning the objects mountedon platforms in a spaced relationship under a vacuum pickup needlelocated in the field of viewof the microscope. Rapid and accuratepositioning is aided by air bearing facilities. One of the platformsincludes a transparent disc for supporting the bottom sides of theobjects. The disc is parallel to and spaced from a mirror which reflectsan image of the bottom sides to the microscope. The microscope is firstraised to its upper position along its principal axis and focused on thetop sides of the objects so that the mirror image of the bottom sides isout of focus and not visible. The top sides are then individuallyinspected. Next, the microscope is moved to its lower position along itsaxis and then focused on the mirror image of the bottom sides of theobjects so that the top sides are out of focus. Preferably, themagnification of the microscope while in its lower position is increasedto provide a larger image of the bottom sides to thereby facilitatetheir inspection. The increasing of the magnification also decreases thedepth of field of the microscope so that an image of the top sides isfar out of focus and therefore not visible. This improves the clarity ofthe image of the bottom sides to further facilitate their inspection.The bottom sides are then individually inspected. During the inspectionthe objects are separated in accordance with certain characteristicswiththe aid of a vacuum pickup needle. The movement of the needle islimited by a ball plunger to prevent damage to the objects.

4 Claims, 9 Drawing Figures PAIENTEB FEB26 I974 SHEET 2 BF 3 PATENTEBFEB 26 I974 SHEET 3 0F 3 mumnum Fla-'8 1 METHODS OF MICROSCOPICALLYINSPECTING OPPOSITE SIDES OF OBJECTS This is a division of applicationSer. No. 30,379 filed Apr. 21, 1970, now U.S. Pat. No. 3,680,947 issuedon Aug. 1, 1972.

BACKGROUND OF THE INVENTION 1. Field This invention relates to methodsof microscopically inspecting a plurality of microscopic objects andmore particularly to methods of individually and microscopicallyinspecting the opposite sides of a plurality of beam-lead integratedcircuits and separating them in accordance with certain characteristics.

2. Prior Art This invention is particularly suited for use in themanufacture of small, fragile objects such as semiconductor devicesor'the like. An example of such semiconductor device which is extremelysmall and fragile is the so-called beam-lead integrated circuit, such asdisclosed in M. P. Lepselter U. S. Pat. Nos. 3,287,612; 3,335,338 and3,426,252.

While the invention is adapted to be used in conjunction with inspectingany small objects, it will be particularly described with respect tobeam-lead integrated circuits. A beam-lead integrated circuit includes asemiconductor body with interconnected circuit element inseparablyassociated on or within such body. Leads are bonded to the body as anintegral part of the device and extend from the body like cantileverbeams to form both electrical and mechanical connections to a header ora circuit pattern formed on a substrate.

In the manufacture of beamlead integrated circuits,

it is necessary to inspect both sides of the circuits with a microscopeto separate the defective devices from the good ones.

In the past much difficulty was experienced in positioning the circuitsunder a vacuum pickup needle located in the field of view of themicroscope. Usually the circuits were supported on a platform slidablymounted on a base and when the operator attempted to move the circuitsunder the pickup needle, he would frequently undershoot or overshoot theneedle. This undershooting or overshooting was exaggerated by themagnification of the microscope. As a result, much time was consumed ineventually positioning the circuits, and therefore in inspecting thecircuits.

Also, much time was consumed in inspecting both the active sides as wellas the inactive sides of the circuits. Either. the circuits had to bemanually turned overto inspect the active sides or a mirror had to bearranged beneath the circuits and the microscope had to be tilted aboutits axis to inspect such active sides. Further, these prior techniquespermitted the inspection of only one circuit at a time with separatehandling steps between each inspection. Moreover, these techniques hadthe disadvantage of not being readily adaptable to the rapid inspectionof an array of a large number of the circuits.

Further, difficulty had been experienced in handling the circuits due totheir smallness in size and their fragility. For example, a slightpressure on the beam leads may bend them so as to make the circuitsunusable in subsequent manufacturing operations. Also, excessivepressures on the semiconductor bodies of the circuits may crush them orotherwise damage them.

SUMMARY OF THE INVENTION It is, therefore, an objective of thisinvention to provide new and improved methods of inspecting a pluralityof microscopic objects.

A further objective of this invention is to provide an arrangement of amicroscope and a mirror located be neath an array of objects to bemicroscopically inspected, wherein the microscope has an upper positionalong its principal axis for the inspection of the top sides of theobjects and a lower position along such axis for the inspection ofreflected images of the bottom sides of the objects.

With these and other objectives in view, the present inventioncontemplates a new and improved method of inspecting an object whichincludes the steps of supporting the object with its top side facing amicroscope having a principal axis and an upper and a lower positionaligned along such axis, and with the bottom side of the object on atransparent member spaced from a reflective surface to reflect an imageof such bottom side to the microscope. The microscope is raised to itsupper position and focused on the top side of the object so that thereflected image of the bottom side is out of focus. The top side is theninspected. Next, the microscope is moved to its lower position and themicroscope is focused on the reflected image of the bottom side of theobject so that its top side is out of focus, and such bottom side isthen inspected.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects and advantages of thepresent invention may be more clearly understood by reference to thefollowing detailed description and the accompanying drawings, wherein:

FIG. 1 is a greatly enlarged, perspective view of a beam-lead integratedcircuit which is to be inspected in accordance with the presentinvention;

FIG. 2 is a perspective view of an apparatus for individually inspectingwith a microscope both the active and inactive sides of a plurality ofbeam-lead integrated circuits;

FIG. 3 is a cross-sectional view taken along line 33 of FIG. 2,illustrating the microscope in its upper posi- -tion for individuallyinspecting the inactive sides of the beam-lead integrated circuits;

FIG. 4 is an enlarged top view taken along line 44 of FIG. 3, showingthe inactive sides of the circuits with identifying marks;

FIG. 5 is a cross-sectional view taken along line 5-5 of FIG. 2,illustrating the microscope in its lower position for individuallyinspecting the active sides of the beam-lead integrated circuits;

FIG. 6 is an enlarged top view taken along line 6-6 of FIG. 5, showingthe active sides of the circuit in a highly magnified state;

FIG. 7 is a cross-sectional view taken along line 77 of FIG. 2,illustrating air bearing facilities in their noneffective state;

FIG. 8 is a cross-sectional view taken along line 88 of FIG. 2,illustrating the passageways of the air bearing facility; and

FIG. 9 is a cross-sectional view taken along line 99 of FIG. 2, showingthe ball plunger arrangement.

DETAILED DESCRIPTION Referring now to the drawings, and in particular toF IG. 1, there is shown an object to be inspected which may be abeam-lead integrated circuit, designated generally by the numeral 11.Such circuit 11 includes a semiconductor body 12 having a bottom oractive side 13 and a top or inactive side 14, and a plurality of beamleads 16 extending from the active side 13 of the body 12.

Typically, the integrated circuit 11 is very minute, the semiconductorbody 12 having a square shape, about 15 to 90 mils wide and about only 2mils thick, while the leads 16 are about 9 mils long and 3 mils wide.Usually, the body 12 is made of silicon and the leads 16 are made ofgold. Extremely minute interconnected circuit elements (not shown),usually in the form of gold plated patterns, are formed on the activeside 13 of the integrated circuits 11. These patterns, the leads 16, thebodies 12 and the active and inactive sides 13 and 14 are to be visuallyinspected for defects and accordingly sorted by the apparatus andmethods of the present invention.

The integrated circuits 11 are removably supported on a carrier memberor disc 17 (FIGS. 2 and 3) of a first platform, designated generally bythe numeral 18, with the inactive sides 14 facing up. While the disc 17may be either transparent or opaque, as a matter of convenience the disc17 is formed from a flat sheet of glass and its top surface may becovered with a layer of pressure sensitive, vacuum holding material,such as a silicone resin of the general type sold by the Dow CorningCorporation under the trade designation Sylgard I82. (See W. R. WaneskyUS. Pat. No. 3,632,074.

The carrier disc 17 is fixed to a first retainer 19 which is threadedinto a second retainer 21 so that the distance of the integratedcircuits 11 to a vacuum pickup needle 24 is adjustable simply byrotating the retainer 19 relative to the retainer 21. The vacuum pickupneedle 24 is located under an objective lens 22 of a microscope 23.

The second retainer 21 is rotatably mounted on a slide plate 25 so thatan operator can angularly move the integrated circuits 11 relative tothe objective lens 22. The slide plate 25 is movably mounted on a base26 spaced from the microscope 23 and perpendicular to its principal axis27. The slide plate 25 is used by he operator to position the circuits11 supported on the disc 17 in the field of view of the objective lens22 of the microscope 23.

The microscope 23, which is used to visually inspect the integratedcircuits 11, may be any standard commerical microscope of the typehaving an objective lens with a diameter substantially larger than theintegrated circuits to be inspected. Preferably, the microscope 23 hasan adjustable magnification and is movable along its principal axis 27to an upper and a lower aligned position. As an alternative to beingmovable to such upper and lower positions, the microscope 23 may befixed on its axis 27 and facilities may be provided for moving theintegrated circuits 11 to an upper and a lower aligned position underthe microscope 23. Advantageously, the microscope 23 is of the type soldby the American Optical Corporation under the trade designationCycloptic Series 53" which has a working distance (object to objectivelens) of about 4 inches and an adjustable magnification of 10X to 40X.

In a typical example of rapidly and accurately inspecting the inactivesides 14 in accordance with this invention l) the bodies 12 of thecircuits 1] are square shaped and have sides measuring approximately 50mils, (2) the microscope 23 is in its upper position and has about a4-inch working distance and 10X magnification, and (3) the circuits 11are located about 4 inches from the lens 22.

The microscope 23 is mounted to the base 26 by conventional attachingmeans. Such microscope 23 has a first knob 28 for controlling itsmagnification and a second knob 29 for moving it along its principalaxis 27 to its upper position as shown in FIG. 3 and to its lowerposition as shown in FIG. 5. The knob 29 is also used to focus themicroscope 23 in these positions.

A second platform, designated generally by the numeral 30, is alsomounted to the slide plate 25 and is spaced a microscopic distance fromthe first platform 18, as shown in FIG. 2. The platform 30 includes atransparent carrier member or disc 31, FIGS. 2 and 5, for removablysupporting the integrated circuits 11 in a spaced relationship withtheir inactive sides 14 facing up. Preferably, the disc 31 is formedfrom a flat sheet of glass and its top surface is covered with atransparent layer of the aforementioned pressure sensitive, vacuumholding material. Also, the disc 31 preferably has a grid 32 formedthereon to aid the operator in positioning the integrated circuits 11 onthe carrier disc 31 in a spaced relationship as shown in FIGS. 2, 5 and6.

The carrier disc 31 is fixed to a third retainer 33 which is threadedinto a fourth retainer 34 50 that the distance of the integratedcircuits 11 to the vacuum pickup needle 24 is adjustable simply byrotating the retainer 33 relative to the retainer 34. The retainer 34 isrotatably mounted to the slide plate 25 so that the operator canangularly adjust the circuits 11 relative to the objective lens 22. Theslide plate 25 is also used by the operator to position the integratedcircuits l1 supported on the disc 31 under the needle 24 located in thefield of view of the objective lens 22.

A mirror 35 is located within the retainer 34 beneath and parallel tothe carrier disc 31. The mirror 35 refleets images of the active sides13 of the integrated circuits 11 to the microscope 23. Advantageously,the mirror 35 is formed from a flat, highly polished silicon slice whichhas the apperance of a black mirror and provides excellent contrast forthe widening of the gold leads 16.

The mirror 35 permits the active sides 13 of the integrated circuits 11to be individually inspected by the operator with the microscope 23simply by rotating the knob 29. This moves the microscope 23 to itslower position along its principal axis 27, as shown in FIG. 5, andpermits the focusing of it on the mirror images of such active sides 13.With the microscope 23 in this position, its magnification is preferablygreatly increased to provide'a larger image of the active sides 13 andthereby facilitate their inspection. This increasing the magnificationalso decreases the depth of field of the microscope 23 so that theinactive sides 14 are far out of focus and therefore not visible. Thisimproves the clarity of the image of the active sides 13. In effect, thesides 14 merely decrease some of the light entering the objective lens22. In other words, when the operator is looking through the microscope23, he is looking through the space between the circuits 11.

In a typical example of inspecting the active sides 13 in accordancewith this invention, (1) the bodies 12 of the circuits 11 are squareshaped and have sides measuring approximately 50 mils, (2) themicroscope 23 is in its lower position and has about a 4-inch workingdistance and a 40X magnification, (3) the circuits 11 are located about3 inches from the lens 22, (4) the mirror 35 is located about 5% inchfrom the disc 31, and (5) the circuits 11 are centered inside thesquares formed by the grid 32 which has openings measuring approximatelyI00 mils.

By the use of this arrangement, both the active and inactive sides 13and 14 of the circuits 11 can be inspected without manually turning thecircuits 11 over and without tilting the microscope 23. Thus, theoperator can rapidly and accurately inspect a large array of thecircuits 11.

Air bearing facilities are provided to minimize the differences betweenthe static and sliding friction of the slide plate 25 on the base 26.Such facilities enable the operator, taking hold of the left end of theplate 25, to overcome the problem of undershooting or overshooting thevacuum pickup needle 24 in the process of positioning the integratedcircuits 11 under such needle 24.

Unwanted rotational movement of the plate is also reduced. Theseproblems are particularly troublesome when viewing the circuits 11 withthe microscope 23 because small movements are greatly exaggerated by themagnification of such microscope 23. By overcoming these problems theoperator can move the slide plate 25 both macroscopic and microscopicdistances. The microscopic distances may be as small as about 1 mil. Asa result the operator can rapidly and accurately position the integratedcircuits ll beneath the vacuum pickup needle 24 and, therefore, rapidlyand accurately inspect large quantities of the integrated circuits 11.

The air bearing facilities include a source 36 'of air under pressureconnected by a flexible tube 37 to a longitudinally extending passageway38, FIG. 8, in the slide plate 25. The passageway 38 communicates with alaterally extending passageway 39, FIG. 7, which in turn communicateswith a vertical passageway 40, one end of which forms an aperture 41 inthe bottom of the plate 25.

A housing 42, FIGS. 2 and 8, is fixed to the left end of the slide plate25 and has a passageway 43, FIG. 8, formed therein, one end of whichcommunicates with the other end of the longitudinal passageway 38 andthe other end of which forms a port 44 in the housing 42.

The port 44 is selectively blockable by the operator to force the airfrom the source 36 out of the aperture 40 in the bottom of the plate 25to thereby float the plate 25 out of contact with the base 26 on asubstantially frictionless air film. With the plate 25 so floating,theoperator can controllably move it very minute distances to veryrapidly and therefore accurately position the integrated circuits 11under the vacuum pickup needle 24. Also, the operator can control theamount of friction between the slide plate 25 and the base 26 bypartially blocking the port 44 to thereby provide greater control overthe movement of the plate 25 on the base 26.

.The vacuum pickup needle 24 is mounted to the base 26 for movementsubstantially perpendicular to the integrated circuits 11 on carrierdiscs 17 and so that such needle 24 can be used to pick up the circuits1]. Such mounting of the needle 24 is accomplished with a standardcommerical micropositioner, designated generally by the numeral 47.Advantageously, the micropositioner 47 may be of the type designatedModel F and manufactured by the Line Tool Company of Allentown,Pennsylvania.

The micropositioner 47 includes a chuck 48 for removably holding theneedle 24 and for providing a passageway 49 communicating with that ofthe needle 24. The needle 24 is preferably coated with a flat blackpaint to render it unobtrusive and to prevent glare when viewedsimultaneously with the integrated circuts 11 through the microscope 23.Also, when the circuits 11 are viewed, the needle 24 is out of focus andtherefore does not interfere with the inspection of the circuits 11.

The chuck 48 is fixed to a housing 51 which also has a passageway 52communicating with the passageway 49 of the chuck 48. One end of a tube53 for providing a vacuum from the source 54 to the needle 24 is fixedto the housing 51 in communication with the passageway 52 therein. Theother end of the tube 53 is fixed to a handle 56 pivotally mounted to abase plate 57 for moving the needle 24 substantially perpendicular tothe integrated circuits 1] on the platform 18 and 30. The base plate 57is fixed to the base 26.

The handle 56 has a first passageway 58, one end of which communicateswith that of the tube 53 and the other end of which communicates withthat of another tube 59 connected to the vacuum source 54. Intersectingthe passageway 58 is a second passageway 61 in the handle 56. The secondpassageway 61 has a port 62 on the top surface of the handle 56, overwhich the operator can place his finger to control the vacuum at thefree end of the needle 24 to pick up the integrated circuits 11. (For asimilar device having a port which isselectively coverable to apply avacuum to a needle to pick up semiconductors, see in J. E. Beroset US.Pat. No. 3,281,692.) If the operator quickly uncovers the ports 62, therushing in of air to the needle 24 produces a puff of air at the freeend of the needle 24, thereby ejecting a circuit 11 that may stick tothe needle 24.

The housing 51 is fixed to a slide 63 of the micropositioner 47 which ismounted on linear slide bearings for vertical movement in a retainingplate 64 fixed to the base plate 57. A stop 65 is mounted to theretaining plate 64 for limiting the upper movement of the slide 63. Thevertical position of the stop 65 is adjustable by a micrometer head 66.

A tension spring 67, FIG. 9, connected to the slide 63 and the retainingplate 64 normally holds the slide 63 up against the stop 65 and thehandle 56 in its upper position, as shown in FIG. 2.

A ball plunger 68, FIGS. 2 and 9, mounted in a housing 69 threaded intothe slide 63 is normally urged downward, as shown in FIG. 2, by acompression spring 71. The extension of the plunger 68 is adjustable bya set screw 72 threaded in the slide 63. The ball plunger 68 limits thedownward motion of the handle 56 so that when the needle 24 ispositioned over the integrated circuits 11, the end of the needle 24does not strike and, as a result, does not damage the circuit 11. Thislimiting action on the handle 56 is particularly important, because theoperator is viewing the circuits 11 is looking straight down,perpendicular to the circuits l1 and parallel to the working end of theneedle 24, and therefore cannot set such end approach the circuits 11.The limiting action is also particularly important when the operator isviewing the active sides 13 of the circuits 11 because the free end ofthe needle 24 is completely invisible, as shown in FIG. 6. Hence, thefeel of the ball plunger 68 striking the base 26 is an indication to theoperator that the end of the needle 24 is very close to the circuit 11and that any additional movement of the needle 24 must be slight so asnot to damage the circuits ,11.

A spot illuminator 76 is mounted adjacent the microscope 23 and itslight beam is reflected off the mirror 35 and onto the active sides 13of the integrated circuits 11. The illuminator 76 aids in providing abright, clear and easily inspected image of the active sides 13 of thecircuits 11 by eliminating a hazy image of the opposite inactive sides14, apparently caused by incident light reflections off of such inactivesides 14 which are face up on the carrier disc 31. The incident angle ofthe light beam is relatively shallow (less than about 45) so that thelight beam reflected off the mirror 35 does not enter the objective lens22 of the microscope.

Operation While the slide plate rests on the base 26, air from 44 forcesthe air from the passageway 38 through passageway 39 and 40 and out ofthe aperture 41 in the bottom of the slide plate 25. As a result, theslide plate 25 floats out of contact with the base 26 on a substantiallyfrictionless air film to permit carefully controllable sliding movementof the plate 25.

The operator then moves the slide plate 25 macroscopic an microscopicdistances to position the integrated circuits 11 supported on the disc17 of the first platform 18 under the vacuum pickup needle 24 and in thefield of view the objective lens 22 of the microscope 23. Initially, itis assumed that the microscope 23 is in its upper position along itsprincipal axis 27, as shown in FIG. 3 and that its magnification is 10Xto provide a large field of view. After so moving the first platform 18,the operator looks through the microscope 23 and individually inspectsthe inactive sides 14 of the integrated circuits 11.

At this time, the opertor views the integrated circuits 11 in thearrangement shown in FIG. 4 and performs a first visual inspection ofthe circuits 11. As he views the circuits 11, he sees that some of themhave and some do not have ink dots 77 thereon. The disk dots 77 indicatethat the circuits 11 are defective as a result of previous tests. Suchdefective circuits 11 are not further inspected and are simply leftresting on the carrier disc 17 of the first platform 18.

On the other hand, the inactive sides 14 of the circuits 11 not havingthe ink dots 77 thereon are further inspected through the microscope 23for any mechanical defects, such as cracks in the silicon body 12, underor over etching the leads 16 that are bent. v

If a particular circuit 11 does not have ink dots 77 thereon and passesthe first inspection, the operator takes hold of the handle 56 with hisright hand (not shown) and places his finger over the port 62 to producea vacuum from the source 54 at the free end of the needle 24. I

The operator then depresses the handle 56 moving the needle 24 towardthe circuit 11, until the ball plunger 68 strikes the base 26. Theincreased pressure on the handle 56 due to the ball plunger 68 strikingthe base 26 indicates to the operator that the needle 24 is very closeto the circuits 11 and that any additional pressure on the handle mustbe carefully applied so as not to apply excessive pressure to thecircuits l1 and thereby damage them. The vacuum from the'needle 24should draw up the circuit 11 thereto. However,'if this does not happen,the operator places a slightly increased pressure on the handle 56pushing the ball plunger 68 against its compression spring 71 therebymoving the needle 24 even closer to, but still not in contact with, thecircuit 11 to draw it up to the needle 24.

Next, the operator while still looking through the microscope 23, whilestill holding the slide plate 25 with his left hand while still blockingthe ports 44 and 62, moves the slide plate 25 to position thetransparent carrier disc 31 of the second platform 30 in the field ofview of the microscope 23. The operator then carefully moves the slideplate 25 in very small increments until the circuit 11 held by theneedle 24 is precisely centered inside the square of the grid 32.

After this centering, the operator quickly uncovers the port 62,permitting air to rush into the needle 24. This produces a puff at thefree end of the needle 24 which ejects the circuit 11 onto the carrierdisc 31 of this second platform 30. At this time, the operator releasesthe handle 56 allowing it to return to its upperward positionas shown inFIG. 2.

Then, the operator rotates the knob 28 to increase the magnification ofthe microscope 23 to 40X and performs a second inspection of the sameinactive side 14 chanical defects. The higher magnification facilitatesthe finding of these defects. The higher magnification also decreasesthe depth of field of the microscope 23.

Next, the operator rotates the knob 29 to move the microscope 23 to itslower position along its axis 27, as shown in FIG. 5, and he focuses themicroscope 23 on the image reflected by the mirror 35 of the active side13 of the circuit 11 being inspected. This places the inactive side 14outside of the now decreased depth of field of the microscope 23 andrenders the side 14 invisible.

At this time, the operator performs a third visual inspection of thecircuit 11, but this time of the more crit ical active side 13 ratherthan the inactive side 14. The operator again looks for theaforementioned mechanical defects. Since the is now viewing the circuitelements of the side 13, he also looks for smeared elements (usually inthe form of gold), foreign particles, and under and over etching of suchelements.

If the integrated circuit 11 undergoing inspection is found to besatisfactory, it is simply left on the carrier disc 31. However, if thecircuit 1] fails to pass the third inspection, it is removed from thecarrier disc 31 ofthe second platform 30 and replaced on the carrierdisc 17 of the first platform 18.

It should be noted that the first inspection can be eliminated and theoperator can simply perform all the other inspections of the integratedcircuits 11 on the second platform 30.

While the invention has been described in connection with the inspectionof a plurality of microscopic objects such as the beam-lead integratedcircuits 11, it

should be understood that the invention may be also used to inspect asingle object, including its top and bottom sides.

What is claimed is: g

l. A method for inspecting an object for a first and a secondcharacteristic, which comprises the steps of:

supporting the object on a first platform;

positioning the first platform with the object thereon to locate theobject within the field of view of a microscope having a principal axisand an upper and an aligned lower position along such axis;

moving the microscope along its axis to its upper position to focus iton the top side of the object to inspect it for the first and the secondcharacteristic;

if the top side of the object has the second characteristic, leaving iton the first platform, while if the top side has the firstcharacteristic, the method further comprising: 7

picking up the object from the first platform;

moving under the picked-up object a second transparent platform that isvertically spaced from a reflective surface and laterally spaced fromthe first platform;

depositing the object on the second platform;

positioning the second platform with the object thereon to locate theobject within the field of view of the microscope;

reflecting an image of the bottom side of the object to the microscope;

moving the microscope along its axis to its lower position to focus iton the reflected image of the bottom side of the object so that its topside is out of focus to inspect such bottom side for the first and thesecond characteristic;

if the bottom side has the first characteristic, leaving it on thesecond platform, while if the bottom side has the second characteristic,the method further comprising: picking up the object from the secondplatform;

moving under the picked-up object the first platform; and

depositing the object on the first platform, whereby both sides of theobject are inspected for the first and the second characteristic from asingle axial position of the microscope and the object is deposited onthe second platform if its top and bottom sides have the firstcharacteristic. v

2. The method as recited in claim 1, further comprising the steps of:

decreasing the magnification of the microscope after it is raised to itsupper position; and

increasing the magnification of the microscope after it is moved to itslower position.

3. The method as recited in cla m -1 further comprising movingadditional objects into the field of the microscope.

4. A method of inspecting a plurality of objects and separating them inaccordance with a first and second characteristic, which comprises:

supporting the objects on a platform; moving the objects supported onthe platform in the field of view of a microscope and beneath a vacuumpickup needle, said microscope having a principal axis and an upper andan aligned lower position along such axis;

raising the microscope to its upper position to focus the microscope onand to inspect each top side of the objects; moving the needlesuccessively toward each object,

the top side of which has the first characteristic, to

draw it up from the platform and hold it by the needle;

releasing the vacuum in the needle and to successively deposit each heldobject on a transparent disc laterally spaced from the platform andvertically spaced from a reflective surface;

moving each object on the transparent disc into the field of view of themicroscope;

reflecting an image of the bottom side of each object from thereflecting surface to the microscope;

lowering the microscope to its lower position to focus the microscope onthe image of the bottom side of each object so that the top side ofeachobject is out of focus and to thereby inspect each bottom side of eachobject;

moving the needle successively toward each object,

the bottom side of which has the second characteristic, to draw it upfrom the disc and hold it by the needle; and

releasing the vacuum in the needle to successively deposit each heldobject, the bottom side of which has the second characteristic, on theplatform, whereby the objects are deposited on the disc only if boththeir top and bottom sides have the first characteristic.

L-566-PT UNITED STATES PATENT OFFICE- CERTIFICATE OF CORRECTION3,794,404 Daed Februarv 26. 1974 Patent No.

Inventor) WILLIAM R. WANESKY It is certified that ext-o; appears in theabove'identified patent and that said Letters Patent are herebycorrected as shown below; v p p Column 4, line 45 (Spec. page 8, line 9)"widening" should be "viewing", I

Co lumn 6 l ine 6 l- (S pec-. page line 16) "is" should bef-r-in I IColumn ,8, line 5]. (Specpage 15, line 29') "the" should be---he- 4 shoul'd be --of-. I I I 4 4 U Claim 4, l'ine 12 (Spec, claim 19, 4 2)either I 4 fand a-- was omitted.

Signed "and sealed this-118th. d perv June; 19m, v

'- (SEAL) 'Attest: I V p p I.

EDWARD ummmm; e c. MARSHALIIDANN Attesting Officer Commissioner ofPatents I

1. A method for inspecting an object for a first and a secondcharacteristic, which comprises the steps of: supporting the object on afirst platform; positioning the first platform with the object thereonto locate the object within the field of view of a microscope having aprincipal axis and an upper and an aligned lower position along suchaxis; moving the microscope along its axis to its upper position tofocus it on the top side of the object to inspect it for the first andthe second characteristic; if the top side of the object has the secondcharacteristic, leaving it on the first platform, while if the top sidehas the first characteristic, the method further comprising: picking upthe object from the first platform; moving under the picked-up object asecond transparent platform that is vertically spaced from a reflectivesurface and laterally spaced from the first platform; depositing theobject on the second platform; positioning the second platform with theobject thereon to locate the object within the field of view of themicroscope; reflecting an image of the bottom side of the object to themicroscope; moving the microscope along its axis to its lower positionto focus it on the reflected image of the bottom side of the object sothat its top side is out of focus to inspect such bottom side for thefirst and the second characteristic; if the bottom side has the firstcharacteristic, leaving it on the second platform, while if the bottomside has the second characteristic, the method further comprising:picking up the object from the second platform; moving under thepicked-up object the first platform; and depositing the object on thefirst platform, whereby both sides of the object are inspected for thefirst and the second characteristic from a single axial position of themicroscope and the object is deposited on the second platform if its topand bottom sides have the first characteristic.
 2. The method as recitedin claim 1, further comprising the steps of: decreasing themagnification of the microscope after it is raised to its upperposition; and increasing the magnification of the microscope after it ismoved to its lower position.
 3. The method as recited in claim 1 furthercomprising moving additional objects into the field of the microscope.4. A method of inspecting a plurality of objects and separating them inaccordance with a first and second characteristic, which comprises:supporting the objects on a platform; moving the objects supported onthe platform in the field of view of a microscope and beneath a vacuumpickup needle, said microscope having a principal axis and an upper andan aligned lower position along such axis; raising the microscope to itsupper position to focus the microscope on and to inspect each top sideof the objects; moving the needle successively toward each object, thetop side of which has the first characteristic, to draw it up from theplatform and hold it by the needle; releasing the vacuum in the needleand to successively deposit each held object on a transparent disclaterally spaced from the platform and vertically spaced from areflective surface; moving each object on the transparent disc into thefield of view of the microscope; reflecting an image of the bottom sideof each object from the reflecting surface to the microscope; loweringthe microscope to its lower position to focus the microscope on theimage of the bottom side of each object so that the top side of eachobject is out of focus and to thereby inspect each bottom side of eachobject; moving the needle successively toward each object, the bottomside of which has the second characteristic, to draw it up from the discand hold it by the needle; and releasing the vacuum in the needle tosuccessively deposit each held object, the bottom side of which has thesecond characteristic, on the platform, whereby the objects aredeposited on the disc only if both their top and bottom sides have thefirst characteristic.